Demountable high-vacuum hotcathode rectifier



F. Bamm vv2,390,683 DEMOUNTABLE HIG-I- VACUUMv HOT-CATHODE RECTIFIER Dec. 11", 1945.

Filed April 24, 1943 Fi .4. 4. LI J Patented Dec. 11, 1945 DEMOUNTABLE HIGH-VACUUM HOT- CATHODE RECTIFIER Fritz Beldi, Baden, Switzerland, assignor to Aktiengesellschaft Brown,

Baden, Switzerland Boveri & Cie.,

Application April 24, 1943, Serial No. 484,456 In Switzerland February 14, 1942 16 Claims.

In order to increase the output of high vacuum hot cathode rectifiers and at the same time keep their dimensions within reasonable and permissible limits, it is necessary to increase the anode load. The higher current density which thus re.-

sults and the correspond-ing rise in operating temperature which occurs necessitates on the one hand a more intensive cooling of the rectifier and on the other hand a demountable type of rectifier. Joints which are not capable of withstanding high temperatures must therefore be arranged to be beyond the efiective range of the high anode and cathode temperatures and it is also very important that lthe insulation between the anodes and the cathode, including the control grids, is not subjected to too high a temperature. Furthermore care must also be taken that in Ithe case of disturbances where high short-circuit currents and correspondingly strong arc discharges may occur, the discharge does not spread to the joints and insulators.

These aforementioned conditions for increasing the power of a hot cathode high vacuum rectifier can be complied with in a very simple manner when according to the invention the cathode of the rectifier is surrounded by a double ringshaped anode which at the same time can form the walls of the rectifier vessel. By this means the cathode is completely surrounded by metal and the insulators lie beyond the range of action of' the cathode. The cathode together with the control grid is suspended from the bushing insulator, so that there is no leakage insulation between cathode and anode. It is also possible to locate cooling pockets in the immediate vicinity of the anode so that a very intensive and effective cooling can be obtained and the desired increase in anode power achieved.

The objects and advantages of the invention will be apparent from the following specification when taken with the accompanying drawing in which:

Fig. 1 illustrates in diagrammatic form a longitudinal section through a high vacuum rectifier;

Figs. 2 and 3 show details of the hot cathode to an enlarged scale in longitudinal and cross section respectively;

Fig. 4 shows the assembly of the rectifier together with a cooling battery;

Figs. 5 and 6 show in elevation and plan a modified form of the invention for three-phase operation.

In Fig. 1 the cathode rods which are provided with a control grid are designated by the reference numeral I, these rods being equally spaced between the walls 2, 2 of the double ring-shaped anode. These walls 2, 2 at the same time form the cylindrical walls of the rectifier vessel which is closed at its lower end by the annular plate 3 and at the upper end by the cover 4 in a vacuumtight manner. A high-voltage bushing insulator 5 is provided. in the cover 4 for supplying the current to the cathode I which is suspended from this insulator. Cooling pockets or ribs 6 are arranged on the outer Wall 2 of the anode and if -necessary cooling ribs or pockets 1 which have to be subjected to a stream of cooling air can also be provided on the inner wall 2. The entire rectier is mounted by means of supporting insulators 8 on the vacuum pump set 9, whereby part of the insulators 8, as shown in the right half of the figure, are constructed as hollow insulators for the evacuation of the rectifier. In order to protect the supporting insulators 8 'from the effects of high temperatures it is expedient to arrange baffles I0 above the bottom'plate 3 at the points where this plate is in contact with the insulators, these baiiles being artificially cooled if necessary. The bushing insulator 5 and the su-pporting insulators 8 can be provided with control electrodes I I which serve in a known manner to control the voltage gradient.

By suitably xing the distance between the cathode I and the outer and inner anode wall 2 and 2' respectively, it is thus possible to arrange for the anode loading to `correspond to the cooling conditions. Furthermore the usual bushing insulators for the anodes are no longer necessary because the anode also serves as the rectifier vessel. This results in a considerable reduction in the number of joints required and the few joints which are necessary are so located that they are not exposed to any high temperatures.

The cathode of the rectiiier consists of a num- Iber of incandescent elements distributed equally around a circle. One of these elements together with the grid and the cooling system is shown in longitudinal section and cross-section in Figs. 2 and 3 respectively. The hot wires I 4 of the cathode are fixed at their lower end to the insulator I6 by means of a tension device I5 and suspended separately at the upper ends from the insulators I l and I8. The insulators for the incandescent elements are cooled by means of two ring-shaped cooling pipes I9 and 20 respectively, running along the entire circumference of the rectifier, the insulator I'I being xed to the common inlet cooling pipe I9 and the insulator I8 to the common outlet cooling pipe 20. A separate branch pipe 2| is' provided for cooling the lower insulator I6 of each cathode element, this branch pipe being connected on the one hand to the inlet pipe I9 and on the other hand to the outlet pipe 20. A control grid 22 is arranged on the outside of the cooling pipe 2|. The currents leads 23 for the cathode Wires I4 are located between the cooling pipes I9 and 20.

In cases where such a high rectifier output isre-` quired that natural air cooling is inadequate, ef-.

fective cooling can be attained by employing an air-blast cooling system. A further possibility is to use a special cooling plant as shown in Fig: 4. The rectifier here has the same construction as that shown in Fig. 1 andeach vouter and inner wall 2 and 2 of the anode is surrounded by a cooling jacket 24 and 25 respectively, through which a continuous stream of cooling liquid flows,

.Y vsupporting said cathode elements, and a common 'Y cluding a cooling pipe serving as a support forY this cooling liquid being recooled in a cooling battery 26 provided with a fan 21.

Rectiers constructed according to the present linvention can be used very advantageously for three-phase` operation, such a rectifier being shownin Figs. 5 and 6 in elevation and plan Irespectively. The three cathodes 28 can in this case be arranged to form a triangle inside a common vessel which is formed by the double walls 29,- 30 .of a common anode. The outer wall 30' of the rectifier vessel is provided with cooling pockets 3l and is ymounted on the pump casing 33 )bymeans of the supporting insulators 32. The reference numeral 34 Vindicates the bushing insulators for the cathodes 28 and as in the case of the single -phase type 1theseinsulators also serve for the suspension and fixing of the cathodesY together with the associated grids. I'claim: 1. Demountable high-vacuum hot-cathode rec tier of the type including a rectifier vessel, a cover extending over the` top of the Vessel in vacuum-tight manner, a connection from the vessel. to a vacuum pump, and a hot cathode and a grid Within the vessel cooperating with an anode, characterised by the feature that the cathode of the rectifier is surrounded by a double ring-shaped anode Yand is supported by fluid 'coo-led insulators Within the confines anode.

2. Rectier as in claimV l, characterised by the feature that the anode also forms the walls ofthe rectifier vessel.

3. Rectifier as in claim 1, characterisedby the of said feature that the bushing insulator for the cathode; is mounted on the cover of said vessel and serves as a supporting insulatorfor said cathode and for its associated grid. l Y

4. Rectifier kas in claim 1 characterised by the feature that the demountable joints for the rectier are located beyond the effective range of the anode and cathode temperatures. Y

5. Rectifier as in claim l, characterised by the feature that the rectifier vesselis supported upon said vacuum pumpv by a plurality of insulators, at least one of the supporting insulators for the rectifier vessel is hollow to provide said connection from the vessel to the vacuum pump. 6.r Rectifier as in claim 1, characterised by the feature that the outer ring-shaped anode is the outer Wall of the rectifier vessel and provided with coolingY ribs orr pockets.

cooling system for cooling Vsaid cathode-supporting insulators.

9. vRectifier as in claim 1, in combinationwith a cooling system adjacent the cathode and inthe grid surrounding said cathode.

10. In 4a demountable high-vacuum hotcathode rectifier,Y an all metal rectifier casing having inner and Iouter cylindrical Walls defining an annular space, cathode and control grid elements within said ann'ular space, the cylindrical walls constituting the anode' of the rectifier, a

vacuum pump, a vplurality of insulators` supportingv said rectifier casing upon said'vacuum pump, at least one of said supporting insulators being hollow to provide a connection between vsaid rectier casing and said vacuum pump, and baffles between said supporting insulators and said cathode elements. Y c

1,1. In a demountable highevacuumf Vhotcathode rectifier, the'invention as recited in' claim Y l0, wherein said supporting insulatorsfarehollow, and control electrodes are located Within said hollow insulators to establish adesired voltage gradient along said insulators. 1 l

12. In a high-vacuum hot-cathode rectifier, cathode elements adapted. to be heated toyincandescence, lan anode, control grid'elements, insulators supporting said ,cathode elements,` yand a coolingsystem including pipes'onjwhilch said insulators are mounted, and cooling'ypipes located in the space between said cathodeele'lrnentsV and said anode, said cooling pipes ccmprsinglat least a part of said control grid elements.

173.111V a high-vacuum hot-cathode rectiiier,

the' invention 'as recited in claim 12 ,wherein Said cooling pipes are of l U-form andV located .about the respective cathodeelements.

. 14. In a highfvacuum hot-cathode` rectifier, the invention as recited in claim l2 wherein said cooling pipes are of U-form and located' about the respective cathode elements, andl .saidf grid elements include va winding on the outside'of the .several U-forrn cooling pipes. v Y Y,

15. A three-phase hotfcathode `'rectiiiercorvnlprising a double-walledmetallic rectifier vessel, the walls `of the Vessel constituting .a Y'cornmon anode for the several phasesacathodefor each phase located betweenfthe doubler walls ofthe vessel, and a control grid for each catliode.r

16. -In a three-phase,hotcathode rectifier, the

Y invention as recited in claim 15 wherein' said 5 vessel.

double-walled metallic rectifer vessel/is offtriangular shape, one cathode and associated control grid being located `in each side of theY rectifier FRITZBELDI. 

